Chronic Obstructive Pulmonary Disease (COPD) is considered a systemic disease that involves pathology in several extra pulmonary tissues. Systemic features in COPD include chronic low-grade systemic inflammation and altered regulation of protein metabolism, which result initially in muscle atrophy only but in later stages in cachexia. Despite the well-recognized importance of treating cachexia in COPD with appropriate nutrition, current nutritional approaches are only partially successful. We recently observed that in order to enhance protein anabolism, manipulation of the composition of proteins and amino acids in nutrition is required in normal-weight COPD. Cachectic COPD patients are characterized by a decreased muscle protein synthesis and an elevated myofibrillar protein breakdown. A substantial number of these patients, characterized by an enhanced systemic inflammatory response, failed to respond to nutritional therapy, which is of clinical relevance as weight gain to nutritional therapy is a significant, independent predictor of mortality in COPD. Eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) are I-3 fatty acids, known to play an anti- inflammatory role through inhibition of cytokine production. EPA+DHA supplementation has been shown to effectively inhibit weight loss, however, weight and muscle mass gain was not achieved both in cancer and COPD. Factors like the low daily dosage of EPA+DHA, the delayed plasma EPA peak after intake, as well as the absence of anabolic agents like proteins and specific amino acids (ie leucine) might explain that EPA+DHA treatment was unsuccessful. Our hypothesis is that there is a unique combination of EPA+DHA, protein and leucine that maximally will stimulate meal-induced net muscle protein synthesis in cachectic COPD patients. In the first experiment, we will examine whether sip feeding of casein protein is preferable above whey protein in the stimulation of whole body net protein synthesis in cachectic COPD patients and whether adding leucine will be of additional benefit. In the second experiment, it will be examined whether daily ingestion of 4000 mg EPA+DHA as compared to 2000 mg EPA+DHA during 4 weeks in cachectic COPD patients will increase the acute response in muscle net protein synthesis to the optimal nutritional mixture as determined in Aim 1. In the third experiment, it will be examined whether daily ingestion of this combination of optimal nutritional mixture and EPA+DHA, as determined in aim 1 and 2, during 8 weeks in cachectic COPD patients will improve nutritional, functional and global clinical outcome as compared to an isocaloric control meal. The combination of plasma and muscle tissue sampling, stable isotope methodology, and assessment of body composition, functional status and quality of life will enable quantification of all endpoints. The results of this study should provide the basis for a new nutritional formulation to support protein anabolism and improve overall outcome in cachectic patients with Chronic Obstructive Pulmonary Disease. PUBLIC HEALTH RELEVANCE: The results of this study should provide the basis for a new nutritional formulation to support protein anabolism and improve overall outcome in cachectic patients with Chronic Obstructive Pulmonary Disease.